Richard Feynman, the late Nobel Laureate in physics, was once asked by a Caltech faculty member to explain why spin one-half particles obey Fermi Dirac statistics. Rising to the challenge, he said, "I'll prepare a freshman lecture on it." But a few days later he told the faculty member, "You know, I couldn't do it. I couldn't reduce it to the freshman level. That means we really don't understand it."

Goodstein also includes it in his "Special Preface" to the Feynman Lecture Series, dated 1989 as well. SarahLawrence Scott 03:21, 20 January 2007 (UTC)

The "faculty member" was David L. Goodstein, who included it in the book, "Feynman's Lost Lecture: The Motion of Planets Around the Sun", co-authored with his wife Judith R. Goodstein. In Chapter 2 (p45), the book says, "When I (D.L.G) started..." and the story continues through that chapter from that same first person perspective. On p52 the book says:

Feynman was a truly great teacher. He prided himself on being able to devise ways to explain even the most profound ideas to beginning students. Once, I said to him, "Dick, explain to me, so that I can understand it, why spin one-half particles obey Fermi-Dirac statistics." Sizing up his audience perfectly, Feynman said, "I'll prepare a freshman lecture on it." But he came back a few days later to say, "I couldn't do it. I couldn't reduce it to the freshman level. That means we don't really understand it."

I accidentally hit save while I was about to edit a copy of a comment I had pasted into the comment box while reverting the last change:

The comment had been:
(You know what's annoying? Arbitrary bolding of text someone found particularly moving! Why not just bold the entire page? Someone, somewhere, is going to agree that the entire page is moving.)

I had intended to edit it in my reversion to:

You know what's annoying? A blanding of all text to the same level, and the inability to recognize some statements ARE more significant than others. Why not just quote everyone and everything? Because, to paraphrase a recent "Incredible" cartoon: to say everything is special is to say NOTHING is. Some things ARE more notable and more generally noted than others, and I am no disciple of the practice of always blanding everything down to the same level. ~ Achilles

To elaborate a bit. I believe pages are much more attractive and appealing when there is evidence of some actual thought, consideration and selection involved in them, rather than the wholesale gathering of any comments and statements that any half-wit could do. QUOTATION IS THE ART OF SELECTING WHAT SOMEONE SOMEWHERE DOES FIND SIGNIFICANT, and presenting quotes on pages here does involve an intelligent gauging of how significant most people might tend to find them. The option of bolding for emphasis of quotes or sections of quotes that someone finds significant has existed here since early on, and I for one, feel it should continue to be used. Why do we quote Feynman, and not his mother, or his next door neighbor? Because Feynman is known to have stated things that people find important, interesting, and often amusing. ~ Achilles 08:13, 23 Mar 2005 (UTC)

The only problem is that the picture going along with the quote about the electron going in any which way it liked is a picture of a Feynman diagram, which diagrams a particle interaction. His quote is about path integral formulation, which (among a significant amount of other things) helped resolve the problem about single electron interference patterns, in which beams that shot single electrons into a classical Young's double-slit setup produced an interference, which shouldn't happen with single electrons. (All of this can be found in Stephen Hawking's 'A Brief History of Time'.) Instead, [2] here is the relevant picture from Wikipedia. Changing to match.

The diagram suggested has now been used, as more illustrative of the notion; though I had thought even a basic Feynman diagram was sufficient to evoke the concept, the illustration of 3 of the potential paths is far more evocative. ~ Kalki 08:49, 23 June 2006 (UTC)

"Science is a way of trying not to fool yourself. The first principle is that you must not fool yourself, and you are the easiest person to fool."

Feynman certainly said the second sentence: in "Cargo Cult Science" and in "What is and What Should be the Role of Scientific Culture in Modern Society". But I can find no evidence that he said the first sentence, so I'm removing it from the main page. DanStyer (talk) 18:10, 21 February 2014 (UTC)

There seems to be some confusion about what was in Feynman's letter to Cosmology writer Marcus Chown's mother. I've just heard a radio documentary featuring Chown quoting the letter as "Dear Mrs Chown, Ignore your son's attempts to teach you Physics. Physics is not the most important thing, love is. ". Source: http://www.bbc.co.uk/i/ts5mm/ listen from 25:23 (annoyingly, it'll disappear from the BBC site on Saturday evening (on 25/09/10))
(You can find it here http://library.fora.tv/2009/05/23/Marcus_Chown_in_Conversation_with_Fred_Watson at 43:20.~LorraineAM)

I did listen to this program a few months ago, and this is more information to work with in terms of how the statement has come to be paraphrased or misquoted by various individuals, including the recipient, but I believe that I have also actually seen a photograph of the post-card in question which contains the phrase as currently quoted in the article. ~ Kalki (talk · contributions) 03:11, 7 April 2011 (UTC)

The quote, exact words, "If you think you understand quantum mechanics, you don't understand quantum mechanics." is very very widely attributed to Feynman-- at the moment, a full-phrase exact match search on that in Google hits "about 16,500" pages. Skimming them, almost all attribute it to him by name (the remaining few just say "as a famous physicist once said", etc.; none seem to attribute it to anyone else)...

This is absolutely Feynman. He says it in a university lecture called The Character of Physical Law - (Anon 2014)

And the wording is very much in his style, and the content sure is...

And me and about 16,500 of my closest friends think it's an excellent quote!...

But I can't find anywhere that actually gives a source! What to do?

It sounds like something he went around saying. Maybe he could be caught saying it in Six (Not So) Easy Pieces? Or someone could find an actual colleague having written "As Dr. Feynmann often said... [or once said to me, etc.]"?

This is probably a paraphrase of the quote attributed to Niels Bohr: "Anyone who is not shocked by quantum theory has not understood it." ~ Ningauble 15:52, 23 February 2011 (UTC)

I am familiar with this quote, but I'm not sure this is the form I originally heard it in:
"There was a time when the newspapers said that only twelve men understood the theory of relativity. I do not believe there ever was such a time. There might have been a time when only one man did, because he was the only guy who caught on, before he wrote his paper. But after people read the paper a lot of people understood the theory of relativity in some way or other, certainly more than twelve. On the other hand, I think I can safely say that nobody understands quantum mechanics."
http://blogs.discovermagazine.com/cosmicvariance/2011/02/15/is-relativity-hard/

The quote above is earlier than Feynman. It is attributed to Niels Bohr (sorry, this is in Danish (Bohr was Danish, too))
Also found this variation (my translation from Danish: »Hvis man kan sætte sig ind i kvantemekanik uden at blive svimmel, har man ikke forstået noget af det,«) "If you can fathom quantum mechanics without getting dizzy, you don't get it": http://videnskab.dk/teknologi/et-kvantebitte-spring-naermere-supercomputeren
They also have a Feynman-quote in that article

A disputed quote on this page is "Physics is like sex. Sure you can get some interesting results, but that's not why we do it." Somewhere in Leonard Susskind's "The Theoretical Minimum" online lecture series he says something to the effect of "as my friend Dick Feynman used to say, 'physics is to sex as mathematics is to masturbation' - but I think he meant it in the sense that with physics, you're doing it with a partner". I can't remember which lecture this is in though, so it's hard to really source. 94.192.113.3 19:34, 31 December 2012 (UTC)

You have it backwards – it should obviously be "physics is to mathematics as sex is to masturbation", as your way around doesn't even make sense. --Florian Blaschke (talk) 21:40, 19 February 2013 (UTC)

The original way is fine. Analogies satisfy the parallelogram law. A:B::C:D == A:C::B:D --74.66.20.170 02:36, 3 April 2013 (UTC)

That wasn't the point. The original representation satisfies the structure of the analogy, but it doesn't pass the test of being semantically meaningful, as the original poster acknowledged.

I think the original post is correct--the implication is that sex has the potential of producing something, like offspring (physics is practical) while math is rote and serves no purpose outside of itself.

I agree, but I think it's more than that. Reason being that mathematics is rewarding in and of itself, but the true potential lies with physics. Mathematics is like practice for the real thing, i.e., physics. Switch up the terms, and you've got yourself a winner

In what sense is what happens at one place in a string independent of what happens to another point also in the string but distant?

The caltech archives are certainly a fairly reliable source, but this seems only a portion of the blackboard, and it seems much more was written on it beyond this image. ~ ♞☤☮♌Kalki·†·⚓⊙☳☶⚡ 13:21, 15 February 2013 (UTC)

This photo was taken in 1974, which was not near "the time of his death" (1988) DanStyer (talk) 00:24, 6 December 2013 (UTC)

The link above is dead. This link currently works. The title for the 1988 image is: "Richard Feynman's blackboard at time of his death." I find the text there unintelligible.[4] The article sources the quote from a different image,[5], a fuller version of which is linked from a page further on in the index: [6]. The title of this is also "Richard Feynman's blackboard at the time of his death."

The image with the clear text quoted in the article is of the same blackboard, a portion of it it can be seen to the left of the larger blackboard image. The text is unintelligible, but the diagrams below it can be readily recognized, and the detailed, clear image can be seen to match. It is possible that a higher-resolution version of the full blackboard could be obtained from the archive.

Now, DanStyer claimed in 2013 that the photo was taken in 1974, contradicting the source, but gave us no evidence other than his own claim and a date. The quote is widely attributed to Feynman, based on that blackboard photo. However, it's possible that Feynman was quoting someone else. Or not. Until we have better information, the reference must stand, it's adequately supported.

There is more. [7] is a detailed photo of another part of that blackboard (?).

[8] is the section with the quote, and this is, as well, explicitly dated as 1988.

[9]a different blackboard, also dated 1988, and titled "Richard Feynman's blackboard at the time of his death."

Likely: Feynman had more than one blackboard. --Abd (talk) 23:04, 8 September 2015 (UTC)

A nice quote on the nature of physics / science: can't pin-point the source[edit]

"If you want to know the way nature works, we looked at it, carefully, (look at it, see) that's the way it looks! You don't like it..., go somewhere else! To another universe! Where the rules are simpler, philosophically more pleasing, more psychologically easy. I can't help it! OK! If I'm going to tell you honestly what the world looks like to the... human beings who have struggled as hard as they can to understand it, I can only tell you what it looks like."

The source is indicated as 'QED: Photons -- Corpuscles of Light' in the this online comment, however I couldn't really find the exact source.137.250.86.102 19:39, 22 April 2014 (UTC)

I have the same question. I knew Feynman (I was in that two-year series of lectures on Physics at Cal Tech, and this sounds like Feynman, but that does not show it was actually said by him. --Abd (talk) 22:19, 8 September 2015 (UTC)

Maybe you’re referring to the following quote, which he made in his BBC Horizon Interview: “You see, one thing is, I can live with doubt, and uncertainty, and not knowing. I think it’s much more interesting to live, not knowing, than to have answers which might be wrong.” The interview’s here: https://www.youtube.com/watch?v=I1tKEvN3DF0

“In physics the truth is rarely perfectly clear, and that is certainly universally the case in human affairs. Hence, what is not surrounded by uncertainty cannot be the truth.”

Can anyone verify its source, if there is any?

A one-time student of Feynman, the applied mathematician Bill Langford, confirmed in a lecture I attended in c. 2010 that Feynman would say something like this in his lectures at CalTech. The short version of the aphorism is "where there is no uncertainty there cannot be truth."

Imagine how much harder physics would be if electrons had feelings![edit]

This quote is attributed to Feynman several times, but the fact that all websites use exactly the same wording for the attribution "speaking at a Caltech graduation ceremony" makes me sceptical. I cannot find any reliable source for it, providing at least a date of the speech. Or is it a misattribution? Can anyone help? -134.106.122.178 09:04, 17 August 2016 (UTC)

It appears to me that the first incidence of this quote is in Lo, Andrew W. (2010). “Warning: Physics Envy May Be Hazardous to Your Wealth!” In: Journal of Investment Management 8.2, pp. 13–63. (online). All other authors tend to cite Lo or no-one.

A related word is attributed to Murray Gell-Mann: “Imagine how hard physics would be if electrons could think”, as quoted in Page S.E. (1999), “Computational models from A to Z”, in: Complexity, Volume 5, Issue 1, Pages 35–41 with reference to Gell Mann, M. The Quark and the Jaguar: Adventures in the Simple and the Complex; W.H. Freeman: New York, 1994. I have no access to this book, and Page does not provide a page (no pun intended).

Gell-Mann and Feynman are known for their controversies, so this may be the reply of Feynman, but I still doubt it. -134.106.122.178 10:01, 17 August 2016 (UTC)